Recently, the cotton team published a research paper entitled "GhL1L1 affects cell fate specification by regulating GhPIN1-mediated auxin distribution" on the Plant Biotechnology Journal online. This study revealed that the NF-YB transcription factor gene GhLEC1-Like1 (GhL1L1) regulates the molecular mechanism of somatic embryogenesis in cotton by regulating the polarity distribution of auxin.
Somatic embryogenesis (SE) is the process in which plant somatic cells are regenerated into embryos and developed into an intact plant in vitro without double fertilization. Cotton somatic embryogenesis has become the basis of cotton genetic transformation technology and has an important role in the research of its mechanism. This study found that overexpression of GhL1L1 inhibited the initiation and proliferation of non-embryogenic callus, and the polarity of explants was not obvious; overexpression of GhL1L1 promoted the production of embryogenic callus and the development of somatic embryos. The expression levels of the marker genes which accompanied by the formation of embryonal cells GhFUS3 and GhABI3 were significantly increased. The callus proliferation rate of the GhL1L1 interference strain was not significantly different from that of the control. The growth of the explant callus showed significant polar growth, but the time for the embryogenic callus of the GhL1L1 interference strain was significantly delayed. Through the determination of auxin content and the analysis of DR5::GUS hybrid material, it was found that GhL1L1 affected the accumulation and polar distribution of auxin. Furthermore, yeast one-hybrid and dual luciferase reporter assays in vivo revealed that GhL1L1 binds to the G-box component of the GhPP2AA2 promoter region to regulate GhPP2AA2 expression. Protein interaction studies in vivo and in vitro have revealed that GhPP2AA2 has an interaction with GhPIN1 protein that regulate auxin polarity. This study showed that GhL1L1 regulates somatic embryogenesis in cotton by affecting the polarity distribution of auxin.
This research has been supported by the National Key Project of Research and Development Plan (2016YFD0101006) and National R&D Project of Transgenic Crops of Ministry of Science and Technology of China (2016ZX08005-004-002). Dr. Jiao Xu is the first author and Prof. Xianlong Zhang and Prof. Xiyan Yang are the corresponding author.